E+G GN 815.1 Spring plungers  are used as stops as well as thrust elements or ejectors.

Types
– Type ST: Steel, standard spring load
– Type STS: Steel, high spring load
– Type NI: Stainless steel, standard spring load
– Type NIS: Stainless steel, high spring load

Material
Type ST/STS: Housing in Steel, blackened and Ball in Steel, hardened
Type NI/NIS: Housing in Stainless steel AISI 303 and Ball in Stainless steel AISI 420C, hardened

Identification of type STS / NIS: Housing with 2 longitudinal markings

GN 815.1 datasheet